A bee collects nectar from a fruit tree in West Bath, Maine. The number of honeybees has now dwindled to the point where there may not be enough to pollinate some major U.S. crops.

Pat WellenbachAP

According to a new survey of America's beekeepers, almost a third of the country's honeybee colonies did not make it through the winter.

That's been the case, in fact, almost every year since the U.S. Department of Agriculture began this annual survey, six years ago.

Over the past six years, on average, 30 percent of all the honeybee colonies in the U.S. died off over the winter. The worst year was five years ago. Last year was the best: Just 22 percent of the colonies died.

"Last year gave us some hope," says Jeffrey Pettis, research leader of the Agriculture Department's Bee Research Laboratory in Beltsville, Md.

But this year, the death rate was up again: 31 percent.

Six years ago, beekeepers were talking a lot about "colony collapse disorder" — colonies that seemed pretty healthy, but suddenly collapsed. The bees appeared to have flown away, abandoning their hives.

Beekeepers aren't seeing that so much anymore, Pettis says. They're mostly seeing colonies that just dwindle. As the crowd of bees gets smaller, it gets weaker.

"They can't generate heat very well in the spring to rear brood. They can't generate heat to fly," he says.

Farmers who grow crops like almonds, blueberries and apples rely on commercial beekeepers to make sure their crops get pollinated.

But the number of honeybees has now dwindled to the point where there may not be enough to pollinate those crops.

Pettis says that this year, farmers came closer than ever to a true pollination crisis. The only thing that saved part of the almond crop in California was some lovely weather at pollination time.

"We got incredibly good flight weather," Pettis says. "So even those small colonies that can't fly very well in cool weather, they were able to fly because of good weather."

Pettis says beekeepers can afford to lose only about 15 percent of their colonies each year. More than that, and the business won't be viable for long. Some commercial beekeepers are still in business, he says, just because they love it.

"It's just something that gets in your blood, so you don't want to give up. [You say,] 'OK, it's 30 percent this year; I'll do better next year.' We're very much optimists," he says.

Beekeepers have a whole list of reasons for why so many colonies are dying. There's a nasty parasite called the Varroa Mite, which they can't get rid of. There are also bee-killing pesticides. And there are just fewer places in the country where a bee can find plenty of flowering plants that provide nectar and pollen.

That was especially true this past year. The same drought that left Midwestern corn fields parched and wilting also dried up wildflowers and starved the bees.

That was a natural disaster. But May Berenbaum, who chairs the Department of Entomology at the University of Illinois at Urbana-Champaign, says that most of the changes in the landscape are the result of people's decisions about what to do with their land.

"I just wish there were more incentives for people — not just farmers — to plant a more diversified landscape that provides nutritional resources for all kinds of pollinators," she says. "Plant more flowers! And be a little more tolerant of the weeds in the garden."

More controversial is the role of pesticides. Some beekeepers and environmentalists are calling for tighter restrictions on the use of one particular class of pesticides called neonicotinoids. Europe is about to ban some uses of these pesticides. But U.S. farmers and pesticide companies are opposed to any such move here, and the Environmental Protection Agency says it's not yet convinced that this would help bees very much.

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Transcript

ROBERT SIEGEL, HOST:

Almost a third of the country's honeybee colonies did not make it through the winter. That's according to a new survey of America's beekeepers. In fact, that's been the case almost every year for the past six years. Beekeepers say unless someone can help more bees survive, there won't be enough to pollinate America's apples, blueberries and other treasured crops. NPR's Dan Charles reports.

DAN CHARLES, BYLINE: The U.S. Department of Agriculture began this annual nationwide survey six years ago, after beekeepers reported some new and frightening problems with their bees.

JEFFREY PETTIS: Well, we started out literally by phoning beekeepers.

CHARLES: That's Jeffrey Pettis, who's in charge of the USDA's Bee Research Laboratory in Beltsville, Maryland.

Over the past six years, on average, 30 percent of all the honey bee colonies in the U.S. died off over the winter. The worst year was five years ago. Last year was the best, just 22 percent of the colonies died.

PETTIS: The last year gave us some hope. The honey bees were doing better.

CHARLES: But this year, the death rate was up again, 31 percent.

When the survey started, beekeepers talked a lot about Colony Collapse Disorder; colonies that seemed pretty healthy but suddenly collapsed - the bees flew away and didn't come back. Beekeepers are not seeing that so much anymore, Pettis says. They're mostly seeing colonies that just dwindle. As the crowd of bees get smaller, it gets weaker.

PETTIS: They can't generate heat very well in the spring to rear brood. They can't also generate heat to fly.

CHARLES: Farmers, who grow crops like almonds and blueberries and apples rely on commercial beekeepers to make sure their crops get pollinated. This year, Pettis says, we came closer than ever before to a real crisis. The only thing that saved part of the almond crop in California was some lovely weather.

PETTIS: We got incredibly good flight weather, so the bees, even those small colonies that we talked about earlier - the small colonies that can't fly very well even in cool weather, they were able to fly because of good weather.

CHARLES: And the bees reached every tree.

Pettis says beekeepers can really only afford to lose about 15 percent of their colonies each year. More than that and they lose money. Some commercial beekeepers are still in business, he says, just because they love it.

PETTIS: I mean it's just something that gets in your blood, so you know what to give out. You know, OK, its 30 percent loss each year - I'll do better next year. We're very much optimists.

CHARLES: Beekeepers have a whole list of reasons why so many colonies are dying. There's a nasty parasite called the Varroa mite which they can't get rid of; also, bee killing pesticides. And they say there just fewer places in the country where a bee can find plenty of food, plenty of flowering plants that provide nectar and pollen. That was especially true this past year. The same drought that left Midwestern cornfields parched and wilting also dried up wildflowers and starved the bees. That was a natural disaster.

But May Barenboim, a professor of entomology at the University of Illinois, says most of the changes in the landscape are the result of people's decisions about what to do with their land.

MAY BARENBOIN: I just wish there were more incentives for more people, not just farmers, to plant a more diversified landscape that provides nutritional resources for all kinds of pollinators.

CHARLES: So, plant more flowers.

BARENBOIN: Plant more flowers and be a little more tolerant of the weeds in the garden.

CHARLES: What's more controversial is the role of pesticides. Some beekeepers and environmentalists are calling for tighter restrictions on the use of one particular class of pesticides, called neonicotinoids. Europe is about to ban some uses of these pesticides. But U.S. farmers and pesticide companies are opposed to any such move here and the Environmental Protection Agency says it's not yet convinced that this would help the bees very much.

Dan Charles, NPR News.

SIEGEL: It may mean little in the overall picture of bee health, but there are many backyards and rooftops around the U.S. with a hive or two, including here at NPR's new building in Washington, D.C.

(SOUNDBITE OF SWARM OF BEES)

SIEGEL: Our so-called green roof, covered with soil and plants, as of yesterday houses two small wooden hives with over two 20,000 bees. No honey yet, but the bees have inspired an unofficial Twitter feed, @nprbees. Transcript provided by NPR, Copyright NPR.